Benzylation of dialkyl phosphites with dithiourethanes

ABSTRACT

ESTERS OF P-HYDROXYBEZYLPHOSPHONIC ACIDS ARE PREPARED BY REACTING A P-HYDROXYBENZYLDITHIOURETHANS WITH ESTERS OF PHOSPHONIC ACIDS IN THE THE PRESENCE OF A BASE. THE ESTERS OF P-HYDROXYBENZYLPHOSPHONIC ACIDS ARE STABILIZERS FOR POLYMERS.

United States Patent Oflice 3,787,540 BENZYLATION F DIALKYL PHOSPHITESWITH DITHIOURETHANES Andreas Schmidt, Reinach, Kurt Schwarzenbach,Aesch, and Heimo Brunetti, Reinach, Switzerland, assignors to Ciba-GeigyCorporation, Ardsley, N.Y.

No Drawing. Filed May 5, 1972, Ser. No. 250,539 Claims priority,application Switzerland, May 12, 1971, 6,972/71 Int. Cl. C07f 9/40 US.Cl. 260-970 10 Claims ABSTRACT OF THE DISCLOSURE Esters ofp-hydroxybenzylphosphonic acids are prepared by reactingp-hydroxybenzyldithiourethans with esters of phosphonic acids in thepresence of a base. The esters of p-hydroxybenzylphosphonic acids arestabilizers for polymers.

The present invention relates to a process for the manufacture ofcompounds of the Formula I wherein R and R independently of one anotherdenote a straight-chain or branched alkyl group, a cycloalkyl group oran aralkyl group, and R and R independently of one another denote astraight-chain or branched alkyl group, a cycloalkyl group, analkylthioalkyl group, an alkyloxalkyl group, a halogenoalkyl group, analkenyl group, the phenyl group or an alkylphenyl group or togetherdenote the groups CH CH or characterized in that 1 mol of a compound ofthe Formula II wherein R and R have the abovementioned meaning and R andR independently of one another denote a straightchain or branched alkylgroup or together, with inclusion of the nitrogen atom, denote asaturated heterocyclic ring, is reacted with one'mol of a compound ofthe Formula III wherein R and R have the abovementioned meaning, in thepresence of a base.

It is known to manufacture p-hydroxybenzylphosphonates by reaction ofappropriately substituted benzyl halides with trialkyl phosphites in thesense of an Arbusow reaction. In.this, one alkyl group of the phosphiteis split otI as alkyl halide. The removal of the alkyl halide which hasbeen split off from the end product frequently presents difiiculties,especially if a higher alkyl halide such as, for example, octadecylchloride, is concerned.

Against this, the process according to the invention avoids theformation of alkyl halide during the reaction, and this substantiallyfacilitates the purification of the end product. Furthermore, theprocess according to the invention is economically advantageous becausethe dialkyl phosphite used, of the Formula III, is practically 3,787,540Patented Jan. 22, 1974 completely incorporated into the end product ofthe Formula I, whilst according to the previously known process a partof the trialkyl phosphite is lost in the form of the alkyl halide. Thefact that the splitting off of alkyl halide is avoided in the processaccording to the invention also denotes a technological advance inasmuchas alkyl halides, especially lower alkyl halides, must be destroyed bycombustion, and this requires expensive absorption installations toavoid contamination of the atmosphere, because of the halogen content.Finally, the substituted benzyl halides required for the previouslyknown manufacturing process are unstable compounds of poor storage life,whilst the starting products of the Formula II required for the processaccording to the invention are stable compounds which can be stored.

It is furthermore known to manufacture compounds of the Formula I byreaction of appropriately substituted benzyl alcohols with trialkylphosphites or triaryl phosphites, whilst splitting off alcohols orphenols. However, the benzyl alcohols required for this purpose aretechnically not as easily accessible as the starting products of theFormula II required for the process according to the invention.Additionally, what has been stated above applies as regards the moreadvantageous use of dialkyl phosphites according to the process of theinvention.

Finally itis known to manufacture compounds of the Formula I by reactionof appropriately substituted benzyltrialkyl-ammonium iodides withtrialkyl phosphites in the sense of a modified Arbusow reaction.However, the manufacture of the benzyl-trialkyl-ammonium iodidesrequires a further process stage as compared to the starting products ofthe Formula H which can be used in accordance with the invention.Furthermore, this process suffers from the same disadvantages as theArbusow reaction of benzyl halides with trialkyl phosphites, describedabove.

Further general advantages of the process according to the invention arethe relatively low reaction temperatures and the short reaction times,which represses the undesired formation of colored by-products. TheN,N-dialkyldithiocarbamates which are split off during the reaction caneasily be separated off in the form of their watersoluble salts. Thesesplitting products can therefore be isolated and again employed for themanufacture of the starting products of the Formula II, and thisrepresents a further technical advantage. Furthermore, the dialkylphosphites used in the process according to the invention aresubstantially less volatile when compared to the corresponding trialkylphosphites hitherto used, and therefore cause distinctly lessobjectionable odor during the reaction.

According to the invention, compounds of the Formula I in which R and Rindependently of one another denote a straight-chain or branched alkylgroup with 1 to 8 carbon atoms or a cycloalkyl group with 6 to 8 carbonatoms and R and R independently of one another denote a straight-chainor branched alkyl group with 1-22 carbon atoms, the groups (CH S-alkylor 2 2 12 Y wherein the alkyl groups possess 1-8 carbon atoms, analkenyl group with 3 or 4 carbon atoms or the phenyl group, arepreferentially manufactured.

In the preferred embodiment of the processes according to the invention,compounds of the Formula II are used in which R and R independently ofone another denote a straight-chain or branched alkyl group with 1 to 5carbon atoms or together, with inclusion of the nitrogen atom, form ahydrogenated heterocyclic S-membered or 6- membered ring.

Particularly preferentially, compounds of the Formula I in which Rdenotes methyl or branched alkyl with 3-4 carbon atoms, R denotesbranched alkyl with 3 or 4 carbon atoms and R and R denotestraight-chain or branched alkyl groups with 1-22 carbon atoms,propenyl, a C H S--alkyl group with 14-20 carbon atoms or phenyl, aremanufactured according to the invention. Particularly preferentialy,compounds of the Formula II in which R and R denote methyl, ethyl orpropyl or together denote the radical of piperidine are employed for themanufacture of the compounds of the Formula L If R R R R R and Rrepresent alkyl groups, these can, within the framework of the indicatedlimits, be methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, tert.butyl, amyl, tert.amyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl,dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl or docosyl. Thesegroups can also be present as alkyl substituents if R, and R, denotealkylphenyl. If R and R are halogenoalkyl groups, they can be2-chloroethyl. R and R: can also be cyclic alkyl groups with 6 to 8carbon atoms. These can be, for example, cyclohexyl or cyclooctyl; thepreferred cyclic alkyl group is the l-methylcyclohexyl-(l) group. R andR as aralkyl groups can, for example, denote benzyl or a-phenyl-ethyl.If R and R with inclusion of the nitrogen atom, form a heterocyclicS-membered or 6-membered ring, this can be, for example, the radical ofmorpholine or piperidine.

If R is alkylthioalkyl, it can be hexadecylthioethyl, dodecylthioethyl,octylthioethyl, hexylthioethyl, ethylthioethyl, octadecylthiopropyl,dodecylthiopropyl or hexylthio propyl. If R denotes alkyloxyalkyl, itcan be dodecyloxyethyl or octadecyloxyethyl. Rla as alkenyl is, forexample, allyl.

The solvents used in the process according to the invention are, forexample, aromatic hydrocarbons such as benzene or toluene,higher-boiling ethers, such as dioxane or ethylene glycol dimethylether, aliphatic hydrocarbons, or hydrocarbon mixtures such as ligroin.Preferred solvents are ligroin and toluene. Bases used in the processaccording to the invention are, for example, alkali amides, such asLiNH- and NaNH and alcoholates such as NaOCH NaOC H and Mg(OC- H Alkaliamides are preferred.

Examples of compounds of the Formula III are dimethyl, diethyl, dibutyl,dihexyl, di-Z-ethylhexyl, dioctyl, didodecyl, dihexadecyl, dioctadecyl,didocosyl, diphenyl or di-p-octylphenyl phosphite. The startingcompounds of the Formula II can be manufactured from the corresponding2,6-dialkylphenol, formaldehyde, carbon disulphide and a secondaryamine, as described, for example, in US. Pat. 2,757,174.

In the process according to the invention, the reactants of the Formulasl1 and III are advantageously employed in molar ratios. If desired, oneof the two reactants can be used in up to 20% excess. The base isemployed in molar amounts relative to the Compound III.

The temperatures in the process according to the invention are notcritical. They are only important for the speed at which the reactiontakes place. If, for example, the process is carried out at 70 C., thereaction time is between 60 minutes and a few hours. Preferredtemperature ranges are 40-100 C.

The reaction according to the invention is preferably carried out whilstpassing nitrogen or a noble gas through the mixture. The reactionaccording to the invention can for example be carried out by adding thebase to a solution of the Compound III and then adding the Compound 11in the same solvent as the Compound III, at elevated temperature.

The compounds obtained in accordance with the process of the inventionare outstandingly suitable for use as stabilizers against thethermo-oxidative and/or light-induced degradation of monomeric andpolymeric substances, especially for the stabilisation of polypropylene,polyethylene, polyamides, polyurethanes, polyacetals or copolymers ofethylene, propylene and a diene such as, for example, norbornadiene ordicyclopentadiene.

The invention is explained in more detail in the examples which follow.

tertJoutyl 13.8 g. (0.1 mol) of diethyl phosphite are dissolved in 50ml. of ligroin and 3.9 g. (0.1 mol) of sodium amide are added. 36.8 g.(0.1 mol) of N,N-diethyl-dithiocarbamic acid3,S-ditert.butyl-4-hydroxybenzyl ester, dissolved in ml. of hot ligroin,are added dropwise at 60 C. The mixture is kept for 3 hours at 70 C. andis then cooled to room temperature, and 200 ml. of toluene are added.The toluene solution is repeatedly Washed with water and evaporated. Theresidue is recrystallized from ligroin. 27 g. (75%) of4-hydroxy-3,S-ditert.butylbenzylphosphonic acid dialkyl ester of meltingpoint 122 C. ar thus obtained.

If, in this example, the diethyl phosphite is replaced by anequimolecular amount of one of the dialkyl phosphites of the Table 1below and otherwise the same procedure is followed, the4-hydroxy-3,6-ditert.butylbenzylphosphonic acid dialkyl esters havingthe indicated physical data are obtained.

TABLE 1 Data of the resulting 4-hydroxy-3,5-dltert.butylbenzyl- Dialkylphosphite phosphonic acid dialkyl ester CH 0 PRO Melting point -157 C.icnitciiirno Melting point: 45-43 0. Boiling point,

ISO-18d C./0.2 mm. Hg. (CH3=CHCH10)2PHO Boiling point, ISO- C./0.l mm.Hg

29.3 g. (0.05 mol) of dioctadecyl phosphite are dissolved in 100 m1. ofligroin and a suspension of 1.2 g. of sodium methylate in 20 ml. ofligroin is added at 20 C. Thereafter the mixture is heated to 60 C. anda solution of 18.38 g. (0.05 mol) of N,N-diethyl-dithiocarbamic acid3,S-ditert.butylhydroxybenzyl ester in 70 ml. of toluene is addeddropwise. The mixture is now heated for 3 hours at 72 C. and a further1% hours under reflux. After cooling, undissolved matter is filtered oifand the filtrate is concentrated to dryness in vacuo. The residue ischromatographed on silica gel G, using a mixture of 95% of toluene and5% of methanol as the eluting agent. The eluates are evaporated and theproduct is recrystallized from acetone. 4-hydroxy-3,,5-ditert.buty'.lbenzyl-phosphonic acid dioctadecyl ester of meltingpoint 57 C. is thus obtained.

If in this example the dioctadecyl phosphite is replaced by anequimolecular amount of one of the phosphorous acid diesters of Table 2below and otherwise the same procedure is followed, the4-hydroxy-3,S-ditertbutylbenzyl-phosphonic acid diesters having theindicated physical data are obtained:

13.8 g. (0.1 mol) of diethyl phosphite are dissolved in 50 ml. ofligroin and 3.9 g. (0.1 mol) of sodium amide are added. 3 8.2 g. (0.1mol) of morpholyl-dithiocarbamic acid 3,5-ditert.butyl-4-hydroxybenzylester, dissolved in 120 ml. of ligroin, are added dropwise at 60 C. Themixture is kept for 3 hours at 80 C., 200 ml. of toluene are added andthe whole is cooled. The organic phase is repeatedly washed with water,dried and evaporated. The solid which remains is recrystallized fromligroin. 4-hydroxy-3,5-ditert.butylbenzyl-phosphonic acid diethyl esterof melting point 122 C. is thus obtained in a yield of 81%.

EXAMPLE 4 tert.butyl i /P\ 110- CH2-S-CN\ 0 H C2110 tert.butyltert.butyl 0/0 0:11. 130- CHr-P\ OCs a tert.butyl The procedure ofExample 1 is repeated, the diethyl phosphite being replaced by anequimolecular amount of diphenyl phosphite or di-(p-tert.octylphenyl)-phosphite. The4-hydroxy-3,5-ditert.butylbenzyl-phosphonic acid diphenyl ester obtainedin a yield of 73% if the same procedure is followed melts at 135 C.,whilst the 4-hydroxy- 3,S-ditert.butylbenzyl-phosphonic aciddi-(p-tert.octylphenyl) ester is a light yellow glass.

EXAMPLE 5 CH 0 0 CH: CH

7 II /P\ HO- CHg-S-C-N CHaO H CH;

tert.butyl O OCH: T/ H0- CH:-P\

I OCH: tert.butyl 11.0 g. (0.1 mol) of dimethyl phosphite are dissolvedin 50 ml. of toluene and 2.3 g. (0.1 mol) of lithium amide are added. Asolution of 26.5 g. (0.1 mol) of N,N-

dimethyl-dithiocarbamic acid 3-methyl-4-hydroxy-S-tert. butylbenzylester in 100 ml. of toluene is added dropwise at 60 C. The mixture iskept for 3 hours at C. and is then cooled to room temperature andfiltered. The filtrate is repeatedly washed with water, dried andevaporated. The residue is recrystallized from ligroin. 23 g. (81%) of3-methyl-4-hydroxy-S-tert.butylbenzyl-phosphonic acid dimethyl ester ofmelting point 102 C. are thus obtained.

If in this example the dimethyl phosphite is replaced by an equivalentamount of diethyl phosphite and otherwise the same procedure isfollowed, 3-methyl-4-hydroxy 5-tert.butylbenzyl-phosphonic acid diethylester is obtained in a yield of 75% of theory, and with a melting 13.8g. (0.1 mol) of diethyl phosphite are dissolved in 50 ml. of ligroin and3.9 g. (0.1 mol) of sodium amide were added. 34.0 g. (0.1 mol) ofN,N-diethyl-dithiocarbamic acid 3,5-diisopropyl-4-hydroxybenzyl ester,dissolved in ml. of hot ligroin, are added dropwise at 60 C. The mixtureis kept for 3 hours at 70 C. and is then cooled to room temperature andfiltered. The filtrate is repeatedly washed with water and evaporated,and the oily residue is distilled in a high vacuum. 4-hydroxy-3,5-diisopropylbenzyl-phosphonic acid diethyl ester is obtained as acolorless oil of boiling point l62-164 C./0.15 mm. Hg.

We claim:

1. Process for the manufacture of compounds of the formula /0Ra HOCHr-P\ I l OR Ra 4 wherein R and R independently of one another are astraight-chain or branched alkyl group, a cycloalkyl group or an aralkylgroup, and R and R independently of one another are a straight-chain orbranched alkyl group, a cycloalkyl group, an alkylthioalkyl group, analkyloxalkyl group, a halogenoalkyl group, an alkenyl group, the phenylgroup or an alkylphenyl group or together are the groups CH CH or Iwherein 1 mol of a compound of the formula wherein R and R are asdefined above and R and R independently of one another are astraight-chain or branched alkyl group or together, with inclusion ofthe nitrogen atom, are a saturated heterocyclic ring, is reacted withone moi of a compound of the formula wherein R and R are as definedabove, in the presence of a base.

2. Process according to claim 1, wherein lithium amide is used as thebase.

3. Process according to claim 1, wherein sodium amide is used as thebase.

4. Process according to claim 1, wherein sodium methylate is used as the'base.

5. Process according to claim 1, wherein the reaction is carried out inthe presence of molar amounts of a base.

6. Process according to claim 1, wherein R and R independently of oneanother are a straight-chain or branched alkyl group with l to 8 carbonatoms or a cycloalkyl group with 6 to 8 carbon atoms and R and Rindependently of one another are a straight-chain or branched alkylgroup with 1-22 carbon atoms, the Sa1kyl 01' z -Oalkyl groups, whereinthe alkyl groups possess 1-8 carbon atoms, an alkenyl group with 3 or 4carbon atoms or the phenyl group.

7. Process according to claim 1, wherein R and R independently of oneanother are a straight-chain or branched alkyl group with 1 to 8 carbonatoms or a cycloalkyl group with 6 to 8 carbon atoms and R and Rindependently of one another are' a straight-chain or branched alkylgroup with 1-22 carbon atoms or the S-alkyl O1 -O-alkyl groups, whereinthe alkyl groups possess 1-8 carbon atoms.

8. Process according to claim 1, wherein R and R independently of oneanother are alkyl with 1-5 carbon atoms or together, with inclusion ofthe nitrogen atom, form a hydrogenated heterocyclic S-mernbered or 6-membered ring.

9. Process according to claim 6, wherein R is methyl or branched alkylwith 3-4 carbon atoms, R is branched alkyl with 3 or 4 carbon atoms andR and R; are straightchain or branched alkyl groups with 1-22 carbonatoms, propenyl, a C H S-a1kyl group with 14-20 carbon atoms or phenyl.

10. Process according to claim 7, wherein R and R are methyl, ethyl,propyl, isopropyl or together are the radical of piperidine.

References Cited UNITED STATES PATENTS 3,277,214 10/1966 Lorenz 260-970X LEWIS GOTTS, Primary Examiner R. L. RAYMOND, Assistant Examiner US.Cl. X.R. 260-969

